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PubMed2003

[Acclimation of foliar photosynthetic apparatus of three tropical woody species to growth irradiance].

The photosynthetic characteristics and protective role of leaf antioxidant systems were studied for seedlings of three woody species, Anthocephalus chinensis, Barringtonia pendala, Garcinia hanburyi, acclimated to 8%, 25%, 50% of natural sunlight for four months. As growth irradiance increased, the saturation points, the light compensation points of photosynthesis, the maximum net photosynthetic rate, and the non-photochemical quenching efficiency of three species were increased, while the apparent quantum yield (AQY), the effective quantum efficiency (Fv'/Fm'), and the photochemical quenching efficiency (qP) were decreased. In protective enzymes systems, SOD and APX activities increased with increasing growth irradiance, but CAT activity was not consistent with PFD. AsA exhibited the most dramatic increase in response to growth irradiance. It could be concluded that besides the increase in xanthophyll cycle-dependent energy dissipation, the enhancement of leaf antioxidants was also a protective pathway against high light intensity.

Acclimatization↗
PubMed1977

Effect of intravenously infused noradrenaline on the cardiovascular system of cold-acclimated rats.

Total metabolism, body temperature and basic circulatory parameters (the heart rate, blood pressure, blood oxygen content and hind limb blood flow) were measured in anaesthetized cold-acclimated male laboratory rats exposed to the calorigenic action of noradrenaline. In addition, cardiac output, the oxygen extraction coefficient and peripheral vascular resistance were calculated from these data.

Adaptation, Physiological↗
PubMed2003

[Aerobic biodegradation performance of six volatile organic compounds by activated sludge acclimated with toluene].

The degradation performance of six volatile organic compounds (VOCs), toluene, o-xylene, m-xylene, p-xylene, benzene and chlorobenzene by activated sludge acclimated with toluene were studied. The experimental results showed that the biodegradation rates of o-xylene, m-xylene, p-xylene, benzene and chlorobenzene increased with increasing of their initial liquid concentration; when concentrations of o-xylene, m-xylene, p-xylene, benzene and chlorobenzene were less than 149 mg/L, 129 mg/L, 133 mg/L, 234 mg/L and 146 mg/L respectively, neither of them brought any notable inhibition or poisonous effects on microbes, and their aerobic biodegradation accorded with first-order reaction. When concentrations of toluene were more than 85 mg/L, its biodegradation rate didn't increase with increasing of its initial liquid concentration and the biodegradation of toluene accorded with the Monod equation.

Aerobiosis↗
PubMed2004

Effects of 8 days acclimation on biological and performance response in a tropical climate.

BACKGROUND: This study was designed to determine the acclimation process elicited by exposure to a tropical climate. METHODS: Nine triathletes performed 3 outdoor indirect continuous running multistage tests in both thermoneutral and tropical conditions. Before travelling to the tropical area (Martinique Island, FWI), the triathletes performed the thermoneutral test (TN) in 14 degrees C and 45% rh conditions. The tropical tests were performed 2 and 8 days after arrival (T2 and T8, performed at a mean environmental temperature of 33.4 degrees C and 75.5% rh). The day before T8, blood samples were drawn for biochemical analysis. During each test, tympanic temperature, sweat rate, weight loss, heart rate (HR), and performance were recorded. RESULTS: The results demonstrated that: 1) the mean tympanic temperature was greater in T2 (p<0.001) and T8 (p<0.01) than in TN; 2) the mean sweat rate was significantly greater (p<0.001) in T2 and T8 than in TN and significantly greater in T8 than in T2 (p<0.03); 3) the weight loss after trials was significantly greater (p<0.001) in T2 and T8 than in TN and in T8 than in T2 (p<0.04); 4) the mean HR and the HR at rest were significantly greater in T2 than in TN (p<0.001) and T8 (p<0.005); 6) significant reductions were observed in T8 vs TN in red cell count (p<0.05) and plasma proteins (p<0.04), the consequence of a 7.5% plasma volume expansion; and 7) the performance was significantly lower in both T2 (p<0.02) and T8 (p<0.03) than in TN. CONCLUSIONS: We concluded that 8 days exposure to hot/wet conditions induced impairments in physiological responses and performance that were still evident on the 8th day. Further and longer outdoor studies are needed to investigate if return to optimal performance levels after adaptation to hot/wet conditions is possible.

Acclimatization↗
PubMed2004

[Difference in light acclimation mechanisms between light-loving and shade-tolerant ficus species].

The effects of light intensity on photosynthetic characteristics and possible mechanisms of preventing photodamage for two Ficus species seedlings grown under different irradiance were studied in rainy season. Ficus tinctoria Corner. is a sun species. Ficus subulata Bl. is a shade-tolerant species. With the increase of growth light intensity, maximum photosynthetic rate (P(max)), midrib angle (MA), chlorophyll a to b ratio (Chl a/b), carotenoid to chlorophyll ratio (Car/Chl), and thermal dissipation (NPQ) increased, while chlorophyll content and the amount of light harvesting complex of photosystem II decreased in both Ficus species. Those changes could reduce the existence of excessive light energy and ameliorated the extent of photoinhibition of photosynthesis. Under strong irradiance, photosynthetic rate was higher in F. tinctoria grown under 100% and 36% relative irradiance (RI) than in F. subulata, but their thermal dissipation capacity did not differ significantly. The results suggested that under strong irradiance seedlings could reduce excessive light energy through increasing both light energy utilization by photosynthesis and thermal dissipation in F. tinctoria, but through increasing thermal dissipation only in F. subulata. Reducing excessive light energy could protect photosynthetic apparatus from photoinhibition or photodamage. Under low irradiance, excessive light energy was reduced mainly through increasing light energy utilization by photosynthesis in F. tinctoria when grown under 100% and 36% RI and through increasing both photosynthetic utilization and thermal dissipation when grown under 12% and 4% RI, and through increasing thermal dissipation only in F. subulata. The extent of photoinhibition was greater in F. subulata than in F. tinctoria under the same irradiance of leaf surface, while the diurnal changes in photoinhibition was similar between the two species when grown under 100% RI. Under 100% RI, MA is larger in F. subulata than in F. tinctoria, which resulted in a lower leaf surface irradiance in F. subulata than in F. tinctoria. This was the main reason that the two Ficus species showed similar diurnal photoinhibition pattern under 100% RI. Acclimation of MA to irradiance was important to Ficus plants, especially to F. subulata.

Chlorophyll↗
PubMed2004

Microcutting culture and morpho-physiological changes during acclimation in two Lycium chilense cytotypes.

Lycium chilense, a deciduous perennial shrub, is one of the endangered native species of Patagonia due to sheep overgrazing. Chances of recolonization by seeds are scarce due to the limited density of propagules in the soil and very specific requirements for germination. The objective was to develop an in vitro propagation protocol that would help to perform reestablishment of this species in degraded areas of the Patagonian steppe. Seeds came from two provenances with different somatic number due to differences in ploidy level. Defoliated microcuttings were planted in test tubes with different growing media and taken to a growth chamber. Rooting percentage did not differ between origins, but higher values were encountered for medium without hormones. Subcultures increased significantly rooting percentage and reduced time to rooting. The leaves from micropropagated plants were thinner, did not exhibit hairs, and had poorly developed palisade parenchyma and less epicuticular waxes. In vitro leaves had lower stomatal density and their stomata were less functional when compared to acclimated leaves. A repopulation program of Lycium chilense based on microcutting culture, specially using subcultures, is feasible.

Acclimatization↗
PubMed1989

Photoperiod and thermoregulation in vertebrates: body temperature rhythms and thermogenic acclimation.

Evidence has recently begun to accumulate that photoperiodic responses of mammals and birds may affect the control of energy balance and thermoregulation. Exposure to short photoperiod can lower the set point for body temperature regulation in birds and mammals, as well as the voluntarily selected body temperature in ectothermic lizards. This decrease is accompanied by a reorganization of circadian or ultradian rhythms of body temperature, particularly an increase in periods spent at rest with minimum body temperatures. Short photoperiod is also used as an environmental cue for induction of seasonal torpor or facilitation of hibernation. During winter, cold tolerance of small mammals is improved by an increase of nonshivering thermogenesis in brown fat. Thermogenic capacity of brown fat (respiratory enzymes, mitochondria, uncoupling protein) is enhanced in response to short photoperiod. This response is mediated via an increase in the activity of sympathetic innervation in brown fat. Moreover, an exposure to short photoperiod prior to low temperatures may act in preparing brown fat for facilitated thermogenesis during acclimation to cold. This shows that photoperiodic control not only affects energy balance indirectly via the control of reproduction or body mass, but may directly interact with central control of thermoregulation and may influence the process of acclimatization.

Activity Cycles↗
PubMed1988

[Reactive changes in the heat-resistant muscle tissue of lake frogs during heat acclimation].

A study was made of the effect of heat acclimation of animals on the individual changes in the muscle heat resistance in populations of Rana ridibunda belonging to European or Asiatic groups of the species. The relationship between the levels of heat resistance of muscle cells and the value of its changes are the same in the populations of these groups. It is believed that this relationship forms on the level higher than populational one.

Acclimatization↗
PubMed1988

Effects of cold acclimation, cold exposure, and palatability on postprandial thermogenesis in rats.

Groups of rats were maintained at 24 degrees C and 4 degrees C (WA, CA). At each temperature one group was fed a pelleted stock diet, while another was fed in addition, 3 kJ of palatable food at 1-h intervals for a total of 8 h during the day. After 2 weeks the thermogenic response to both 3 kJ and 30 kJ of palatable food was determined by measuring oxygen consumption over a period of 3 h. Food intake revealed two phases of postprandial thermogenesis. During the initial cephalic phase which lasted 30 min the O2 consumption increased by about 40 percent with both test meals and the response was comparable for WA and CA rats tested at the same temperature. During the subsequent gastrointestinal phase the response was proportional to the size of the meal and the CA rats were always more responsive than the WA rats specially when tested at 4 degrees C. The results suggest that postprandial thermogenesis during the initial cephalic phase is related to food palatability and that cold exposure and cold acclimation cause an enhanced response during the second phase of meal thermogenesis.

Acclimatization↗
PubMedDate not supplied

[Effect of prolactin on the phospholipid composition and cholesterol level in liver microsomes of the carp during acclimation to different temperatures].

The phospholipid composition, content of cholesterol and its esters in the carp (Cyprinus carpio L.) liver microsomes depend on the environmental temperature. The free cholesterol amount and cholesterol/phospholipids ratio in microsomes decrease after the lowering of temperature from 20 to 5 degrees C. The temperature elevation to 30 degrees C results in an increase of the cholesterol ester content. The relative proportions of phosphatidyl choline, phosphatidyl ethanolamine, sphingomyelin, phosphatidyl inositol, phosphatidyl serine, phosphatidic acid increase with a significant decrease of the unidentified phospholipids amount at 30 degrees C. Prolactin affects the cholesterol content and phospholipid composition of liver microsomes. The hormone has a more pronounced effect at subextremal temperatures (5 and 30 degrees C). The actions of prolactin and temperature on the cholesterol content are similar. The hormone influence on the membrane phospholipid composition is opposite to the effect of the temperature acclimation. The possible role of prolactin in the temperature adaptation of the membrane lipids metabolism in poikilotherms is discussed.

Acclimatization↗
PubMed1987

Changes in body water and electrolytes during heat acclimation: effects of dietary sodium.

In an effort to describe the influence of both high (HNA) and low (LNA) dietary sodium (399 vs. 98 mEq Na+ X d-1) on body fluids during heat acclimation (HA), nine untrained males underwent 8 d of HA twice (90 min treadmill walking, 5.6 km X h-1, 6% grade) in an environmental chamber (40.1 degrees C, 23.5% RH). Mean wholebody Na+ balance calculations indicated that HNA resulted in an increase of Na+ of $916 mEq per 8 days per subject, whereas LNA resulted in a relative Na+ deficiency of -230 mEq per 8 days per subject. Subjects exhibited typical HA adaptations of decreased heart rate (HR), decreased rectal temperature (Tre) during exercise, and an increase in resting plasma volume (PV) during both diets. Significant HNA vs. LNA differences (p less than 0.05) were observed in HR (days 3-5), Tre (days 3-6), PV (day 4), plasma osmolality (day 4), plasma Na+ (day 4), urine Na+ (days 2-8), and sweat Na+ (days 4 and 8). The between-diet differences in HR, Tre and PV were not detectable by the end of each dietary-exercise regimen. Needle biopsy samples (20-50 mg, lateral aspect of the gastrocnemius) indicated that muscle Na+ and muscle water were similar on all days, except day 9 when intracellular fluid expansion during LNA was noted. Change in body weight was not strongly correlated with delta PV (R2 = 0.47, 0.10) and neither osmotic forces nor plasma protein movements explained all PV shifts adequately.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1985

[Heat sensitivity of the medial preoptic area of the hypothalamus during seasonal adaptation and acclimation to high environmental temperature].

The activation threshold of the vascular heat dissipation response to local heating of the preoptic hypothalamus was studied with respect to year's seasons and in heat acclimation. The seasonal adaptation to high ambient temperature was followed by a shift of the thermal neutrality zone and a related change of the absolute temperature threshold of the heat dissipation response. The latter was triggered throughout the year by a raise of temperature of the medial preoptic area from the initial level by 0.92 +/- 0.07 degrees C on the average. This finding suggests that the relative heat sensitivity of the anterior hypothalamus does not change in adaptation to high ambient temperature.

Acclimatization↗
PubMed1979

Relationships among training, heat acclimation, and heat tolerance in men and women: the controversy revisited.

For more than a decade there has been a controversy over the beneficial effects of physical training in a cool environment on exercise-heat tolerance. The issues include (a) inadequate controls regarding the physical characteristics of subjects, (b) marked variability in the conditions of the standard heat tolerance tests and (c) differences in the intensity and duration of the training programs employed. Intense training in a cool environment cannot serve as a substitute for exercise in the heat if acclimation is desired within a 2 week period. However, a substantial improvement (50%) in heat tolerance can be derived from 8-11 weeks of training under temperate conditions (21 degrees C) and thermal equilibrium can be maintained for at least 4 hours during mild work (200 W/m2) in dry or wet heat by endurance runners. These adjustments occur in both men and women and appear to be independent of aerobic capacity. The key to improved thermal tolerance with training in a cool environment is maintenance of an elevated core temperature for a sufficient duration of time to produce an adaptive response.

Acclimatization↗
PubMed1980

Effects of noradrenaline and the blood perfusion rate on the oxygen consumption of intact and isolated muscles of cold-acclimated rats.

The authors studied the effect of the blood perfusion rate and of noradrenaline (NA) on the oxygen consumption of the isolated hind limb and on the partly - and vascularly completely - isolated cranial gracilis muscle of cold-acclimated rats. Oxygen consumption of the limb was stimulated by a raised perfusion rate together with growth of the oxygen extraction coefficient and by NA, which also raised oxygen consumption when the perfusion rate was constant. Oxygen consumption of the partly isolated muscle was likewise stimulated by a raised perfusion rate, but without a simultaneous increase in the oxygen extraction coefficient. In the vascularly completely isolated muscle, a raised perfusion rate had only a transient stimulant effect on oxygen consumption. In the partly and the completely isolated muscle, NA raised the arteriovenous difference in the blood oxygen content and organ resistance independently of each other. The calorigenic effect of NA, which was determined by the ratio of the two effects, did not exceed 34% above the resting level. The conclusions that the thermogenesis of resting muscle can be controlled by the blood flow on the basis of a mechanism other than the limitation of oxygen or substrates supply, and that NA acts independently of oxygen extraction from the blood and of the blood flow, show the blood flow to be a mechanism at organ level, which participates in the control of nonshivering thermogenesis in skeletal muscle.

Acclimatization↗
PubMed1984

Mechanism for adaptive modification during cold acclimation of phospholipid acyl chain composition in Tetrahymena. I. Principal involvement of deacylation-reacylation.

The purpose of the present studies with in vivo isotope labeling was to explore the mechanism by which the fatty acyl composition of membrane phospholipids was altered quickly after a downward temperature-shift in Tetrahymena pyriformis. 1. When 39 degrees C-grown Tetrahymena cells were shifted to 15 degrees C, unsaturated fatty acids, especially gamma-linolenic acid, were increased, with compensating decrease of palmitic acid in phospholipids. 2. However, in the [32P]Pi-prelabeled cells, the specific radioactivities of major membrane phospholipids, phosphatidylethanolamine, phosphatidylcholine and 2-aminoethylphosphonolipid, were not changed within 10 h after shift-down. Furthermore, in the [14C]palmitic acid-prelabeled cells, the specific radioactivities toward phospholipids also did not change after temperature-shift. 3. After the shift, the rate of incorporation of [14C]acetate into fatty acids was reduced to less than one-tenth and the principal fatty acid newly synthesized was linoleic acid, and palmitic and gamma-linolenic acids were also formed to almost same degree. 4. In contrast, when cells prelabeled with both [32P]Pi and [14C]palmitic acid were shifted to 15 degrees C and then linoleic and gamma-linolenic acids, which are known to increase during cold acclimation, were added to the medium, the 14C/32P ratios of major phospholipids were progressively decreased until 5 h after the shift. These results suggest the mechanism for the alteration of phospholipid fatty acyl composition at lowered growth temperature by which preexisting fatty acids of membrane phospholipids would be deacylated and then, after modification to adequate unsaturated fatty acids by desaturation and/or elongation, be reacylated again into lysophospholipids.

Acclimatization↗
PubMedDate not supplied

Effects of exposure to cold and catecholamines on the respiratory quotient and plasma levels of free fatty acids, glucose and urea in rats acclimated to 15 degrees C.

The reported experiments were carried out on 95 male Wistar rats weighing 300 to 360 g kept for 3 weeks in separate cages in a room at an ambient temperature of 15 degrees C. The rats normally fed or fasted for 24 hours were injected at 24-26 degrees C with adrenaline or noradrenaline (400 micrograms/kg s.c.) or injected at 15 degrees C with propranolol (1 mg/kg s.c.). The metabolic rate (MR), respiratory quotient (RQ) and plasma levels of free fatty acids (FFA), glucose (G) and urea (U) were determined. Similarly as in the non-acclimated rats, the determined parameters considered separately were insufficient for estimating the changes in the catabolism of lipids, carbohydrates and proteins, but a simultaneous determination of the RQ and plasma levels of FFA, G or U with MR measurement indicated the degree of lipid, carbohydrate or protein participation in cold-induced thermogenesis.

Acclimatization↗